THE HUMAN HAIR SYSTEM (Human hair and fingernails)
Hair is a "keratinized" threadlike outgrowth from the skin of mammals. A mammal is an animal in the class Mammalia that are distinguished by having hair, a self-regulating body temperature, and in females they have milk-producing mammary glands to feed their young. Back to the word "keratinized;" keratain is an extremely tough protein substance in your hair, fingernails and skin. When a tissue is "keratinized," it becomes hard or horny, therefore it is called horny tissue (hair, skin and nails).
Human hair is made of the same stuff (keratin) that is found in human fingernails, animal hooves, feathers, antlers, horns, and claws. The body protein, keratin, grows out of a tiny opening in the skin called a follicle.
Human hair is a thin, flexible shaft of horny/hard cells that develops from a cylindrical invagination of the epidermis (top layer of the skin). An invagination means that it is ensheathed in something. Each hair follicle (tiny sac) consists of a free portion of shaft (scapus pili) and a root (radix pili) embedded within the follicle.
While it may seem as though humans are hairless being, this couldn't be further from the truth. All over your body you have hair except of course for your lips and the palms of your hands and soles of your feet. By the time you reach adulthood, you will have at least 5 million hairs growing out of your skin, all over your body. The odd thing is, this is the same as a gorilla, only the gorilla's hair is thick and long. The human hair on the skin is small and thin making it difficult to detect.
The shaft of the hair follicle consists of three layers of cells:
The cuticle or outermost layer
The cortex, forming the main horny portion of the hair
The medulla, which is the central axis
When it comes to getting goosebumps, even though human hair is small and thin making it difficult, it is easy to detect your hair when you get goosebumps. Then you'll really notice how much hair your have. When your body becomes, frightened or startled, you may develop goosebumps. They are tiny and temporary bumps on your skin caused by the contraction of the muscles that are attached to the hair follicles. The muscles will tighten on those hairs and WA-LAH, the hairs will stand upright. In animals, the purpose of goosebumps is to fluff up their fur or feathers. This helps them trap air and creates warmth and it also makes them look bigger and scarier.
Some hair is curly and some hair is straight. This depends on the actual shape of the follicle (little sac) out of which the hair is growing. Straight hair will lay flat because it is round and grows out of round follicles. Curly hair bends and turns because its cross-section is an oval because it grows out of oval follicles.
Some hair is dark, some is white and some hair is completely white or gray. Hair color is dependent on the pigment in the cortex that forms the main horny portion of the hair. Gray or white is simply hair without pigment. This same chemical pigment is what determines our skin color. It is called melanin. Since hair comes out of skin, if you do not have melanin in your body, this gives you white hair; a little more melanin will create a blonde or strawberry blond appearance; more melanin will make you a red-head; and even more melanin will make brown-hair; and further down the line, even more melanin will make your hair black or even blue-black.
JUST THE FACTS:
Hair of the eyebrow lasts only 3 - 5 months.
Hair of the scalp lasts only 2 - 5 years.
About 80 - 100 hairs will fall out of your head every day, and you still have over 100,000 hair follicles left.
Even where it "appears" you have no hair on your body, there are about 5 million of them.
Hair in each part of your body has a definite period of growth after which it will shed.
In the adult human there is a constant and gradual loss and replacement of hair.
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